1. Field of the Invention
The present invention relates to an oil pan structure for an automotive engine.
2. Description of the Prior Art
In most automotive engines now in use, the cylinder block is connected at a rear end with a clutch housing and then with a transmission housing to complete a substantially automotive power plant. The power plant is, therefore, elongated in configuration and is prone to bending under the influence of oscillations and vibrations occurring in the power plant during the operation of the engine.
In order to substantially eliminate, or minimize, the bending of the power plant, or engine bending for short, gusset plates are utilized between the cylinder block and the transmission housing to increase the rigidity of the engine system as a whole. According to the well established automotive practice, the gusset plates are fitted outboard of the engine cylinder and the transmission housing and, therefore, it has long been encountered with a problem in that, since the fitting of the gusset plates outboard of the engine cylinder and the transmission housing imposes limitations to the design of engine layout, not only does the servicing of the engine and its associated parts tend to be hampered, but also the weight of the power plant tends to be increased.
In order to substantially obviate the above problem, U.S. Pat. No. 3,942,502, patented Mar. 9, 1976, discloses a technique wherein the oil pan, secured to the bottom of the cylinder block to define a crankcase in cooperation with the cylinder block, is formed at its rear end with a coupling flange through which the oil pan is connected with the clutch housing. The oil pan is formed with reinforcement ribs on each side thereof to reinforce the connection, and hence to increase the rigidity of connection, between the cylinder block and the clutch housing so that the engine bending can be substantially minimized.
However, it has been found that, since the rear end of the oil pan is connected directly with the clutch housing through the coupling flange according to the above mentioned U.S. patent, not only are complicated and time-consuming fitting procedures required to connect the rear end of the oil pan to the clutch housing, but also the servicing of internal parts of the clutch housing is not easy to accomplish.
While less relevant to the present invention, another approach to minimize the engine bending is to use the crankshaft bearing beam designed to have its rear end adapted to be flangedly connected directly with the transmission housing, such as disclosed in U.S. Pat. No. 4,515,119, patented May 7, 1985.